| Aero-engine is the national comprehensive embodiment of industrial manufacture,science and national defense capability.With the implementation of "two aircraft projects",it is urgent to develop the world’s advanced aero-engine.Aero-engine works in high temperature /high speed environment for a long time.Due to manufacturing installation error,hot deformation,friction and wear of long time running,misalignment of statically indeterminate rotor system(SIRS)is widely existed in aero-engine system failure,and it poses a serious threat to stable operation.At present,the basic theory of SIRS and misalignment/unbalance is seriously inadequate,and it can not meet the needs,so it is urgent to carry out in-depth research work.In this paper,SIRS of aero-engine is taken as research object.The analytical model derivation and experimental verification are carried out for alignment,middle support(MS)misalignment and turbine back support(TBS)misalignment / unbalance.The purpose of this paper is to provide a set of practical and effective theoretical analysis methods and experimental research ideas for design,dynamic modeling and misalignment vibration control of SIRS.(1)Taking the simplified model of SIRS as research object,according to the meshing contact conditions of spline joint(SJ),the meshing stiffness model is deduced,and the approximate rigid meshing state is analyzed to make low-pressure rotor system become statically indeterminate structure.Then,the characteristics of statically indeterminate and elastic supporting structures are considered,and the alignment dynamic model is built by combining force method and D’Alembert principle.The natural frequency and dynamic characteristics of the two models are obtained by simulation.(2)On the basis of the alignment model,the theoretical model of MS misalignment is obtained by removing MS and adding the static misalignment force in SIRS.The flexibility correction coefficient is introduced for the first time,and the theoretical model of MS misalignment is obtained,and the dynamic characteristics of MS misalignment are analyzed.A new law of influence on the natural frequency and rotor dynamic characteristics is obtained.(3)Based on the preceding study,the misalignment is introduced into TBS,and the dynamic additional excitation force and the influence on the stiffness matrix are derived by using the "force method" in detail.The dynamic characteristics of TBS misalignment are obtained.It is found that the misalignment fault will not only produce dynamic additional excitation,but also cause the change of stiffness matrix in SIRS,resulting in the critical speed drift,2× vibration and the "8" shape orbit.The results of follow-up experiments are in good agreement with the theoretical results.(4)For the theoretical analytical model of alignment,MS misalignment and TBS misalignment in SIRS,the confirmatory experiment of inherent characteristics and rotor dynamics characteristics are carried out.It is proved that the established theoretical model can well predict dynamic characteristics and change rule.The research results provide theoretical and experimental basis for the design,dynamic modeling,vibration control and fault diagnosis of SIRS. |
